fgets

The fgets ("file get string") function is similar to the
gets function. This function is deprecated -- that means
it is obsolete and it is strongly suggested you do not use it --
because it is dangerous. It is dangerous because if the input data
contains a null character, you can't tell. Don't use fgets unless
you know the data cannot contain a null. Don't use it to read files
edited by the user because, if the user inserts a null character, you
should either handle it properly or print a clear error message. Always
use getline or getdelim instead of fgets if you
can.

Rather than reading a string from standard input, as gets does,
fgets reads it from a specified stream, up to and including a
newline character. It stores the string in the string variable passed
to it, adding a null character to terminate the string. This function
takes three parameters: the first is the string into which to read data,
the second is the maximum number of characters to read. (You must supply
at least this many characters of space in the string, or your program
will probably crash, but at least the fgets function protects
against overflowing the string and creating a security hazard, unlike
gets.) The third parameter is the stream from which to read.
The number of characters that fgets reads is actually one less
than than number specified; it stores the null character in the extra
character space.

If there is no error, fgets returns the string read as a return
value, which may be discarded. Otherwise, for example if the stream is
already at end of file, it returns a null pointer.

Unfortunately, like the gets function, fgets is
deprecated, in this case because when fgets cannot tell whether a
null character is included in the string it reads. If a null character
is read by fgets, it will be stored in the string along with the
rest of the characters read. Since a null character terminates a string
in C, C will then consider your string to end prematurely, right before
the first null character. Only use fgets if you are certain the
data read cannot contain a null; otherwise, use getline.

Here is a code example that uses fgets. It will create a text
file containing the string Hidee ho! plus a newline, read it back
with fgets, and print it on standard output. Notice that
although 100 characters are allocated for the string my_string,
and requested to be read in the fgets call, there are not that
many characters in the file. The fgets function only reads the
string up to the newline character; the important thing is to allocate
enough space in the string variable to contain the string to be read.